In vertebroplasty, the surgeon seeks to treat a compression fracture of a vertebral body by injecting bone cement such as PMMA into the fracture site. In one clinical report, Jensen et al., AJNR: 18 Nov. 1997, Jensen describes mixing two PMMA precursor components in a dish to produce a viscous bone cement; filling a 10 ml syringe with this cement, injecting the cement from the larger syringe into a plurality of smaller 1 ml syringes, and finally delivering the viscous cement into a desired area of the vertebral body through needles attached to the smaller syringes.
In order to insure that the injected cement does not travel far from its intended placement location, fluoroscopy is often used by the clinician to monitor the location of the injected cement. However, since delivering the cement by a simple syringe requires placing the clinician's hand in the fluoroscopy field, delivering the cement under direct fluroroscopy would cause the clinician to be exposed to significant x-ray radiation within a fluoroscopy field produced by a fluoroscope. Thus, in order to reduce such exposure, the clinician often performs this procedure when the fluoro is turned off, and only monitors the cement location intermittently when safely outside the range of the fluoroscopy field.
In response to these concerns, techniques for allowing the clinician to remain outside of the fluoro field have been developed. These techniques typically involve the use of a long delivery tube, whereby the proximal end of the tube extends from a cement injection means and the distal end is coupled to a hollow bore cannula inserted into the vertebral body. The delivery tube is used as a conduit for delivering the bone cement from the injection means to the cannula for injection into the vertebral body. The additional length of the delivery tube allows the clinician to perform the vertebroplasty procedure at a distance outside the fluoro field.
U.S. Pat. No. 6,348,055 (“Preissman”) discloses a cement delivery system suitable for vertebroplasty involving a high pressure injection gun that delivers cement through a flexible tube and into a rigid cannula inserted in the vertebral body. Preissman also discloses that a stylet made of steel or other suitable metal may be inserted into the cannula for the purpose of penetrating hard tissue. See Priessman at col. 6, lines 28-55.
Preissman does not discloses a flexible stylet, nor does Preissman discloses inserting the stylet into the flexible delivery tube.
U.S. Pat. No. 6,241,734 (“Scribner”) discloses a vertebroplasty cement delivery system having a series of cannulae and a tamping instrument designed to deliver cement into the patient at a pressure of no greater than about 360 psi. The tamping instrument is generally made from rigid, inert plastic or metal material. See Scribner at col. 11, lines 17-18.
PCT Published Patent Application No. WO 00/54705 (“Bhatnagar”) also discloses a vertebroplasty cement delivery system having a series of cannulae and a plunger designed to deliver cement into the patient. Bhatnagar discloses that the injection device can be fabricated from any of a variety of materials, which are compatible for use as surgical instruments, including metallic materials and non-metallic materials such as thermoplastics, ceramic materials, carbon fiber materials and composite materials. See Bhatnagar at page 19, lines 13-20.
U.S. Pat. No. 4,769,011 (“Swaniger”) discloses a syringe apparatus comprising a flexible plunger stem slidably received in barrel. Because this device was designed to delivery granular substances during alveolar ridge augmentation and repair, the barrels are preformed to described arcs similar to that of the alveolar ridge. Swaniger discloses that the barrel is made of glass. See Swaniger at col. 6, line 7.
In sum, all of the prior art systems that use both a delivery tube and stylet disclose either a rigid delivery tube or a rigid stylet.